Backside illuminated image sensor and method of manufacturing the same

ABSTRACT

A backside illuminated image sensor includes a substrate having a frontside surface, a backside surface and a recess formed in a backside surface portion thereof, pixel regions disposed in the substrate, an insulating layer disposed on the frontside surface of the substrate, a bonding pad disposed on a frontside surface of the insulating layer, and a second bonding pad disposed in the recess and electrically connected with the bonding pad.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Korean PatentApplication No. 10-2019-0008296, filed on Jan. 22, 2019, and all thebenefits accruing therefrom under 35 U.S.C. § 119, the contents of whichare incorporated by reference in their entirety.

TECHNICAL FIELD

The instant application relates generally to semiconductor devicemanufacturing and processes thereof. These processes result in noveldevices for use in backside illuminated image sensors.

BACKGROUND

The present disclosure relates to a backside illuminated image sensorand a method of manufacturing the same.

In general, an image sensor is a semiconductor device that converts anoptical image into electrical signals, and may be classified orcategorized as a Charge Coupled Device (CCD) or a Complementary MetalOxide Semiconductor (CMOS) Image Sensor (CIS).

The CIS includes unit pixels, each including a photodiode and MOStransistors. The CIS sequentially detects the electrical signals of theunit pixels using a switching method, thereby forming an image. The CISmay be classified as either a frontside illuminated image sensor or abackside illuminated image sensor.

The backside illuminated image sensor may include pixel regions in asubstrate, transistors formed on a frontside surface of the substrate,an insulating layer formed on the transistors, bonding pads on theinsulating layer, an anti-reflective layer formed on a backside surfaceof the substrate, a light-blocking pattern formed on the anti-reflectivelayer, a planarization layer formed on the light-blocking pattern, acolor filter layer formed on the planarization layer, and micro lensarray formed on the color filter layer.

The bonding pads may be exposed by openings formed through theanti-reflective layer, the substrate and the insulating layer. Further,second bonding pads may be formed on the anti-reflective layer, innerside surfaces of the openings and the bonding pads may be exposed by theopenings, and third bonding pads may be formed on the second bondingpads. Wires may be bonded on the third bonding pads or solder bumps maybe formed on the third bonding pads.

For example, after forming the openings, a first metal layer such as atungsten layer may be formed, and a second metal layer such as analuminum layer may be formed on the first metal layer. The third bondingpads may be formed by patterning the second metal layer, and the secondbonding pads may be formed by patterning the first metal layer.

The light-blocking pattern may be simultaneously formed with the secondbonding pads. For example, after forming the third bonding pads, aphotoresist layer may be formed on the first metal layer and the thirdbonding pads, and a photoresist pattern may then be formed by aphotolithography process. The second bonding pads and the light-blockingpattern may be formed by an anisotropic etching process using thephotoresist pattern as an etching mask. In this case, a thickness ofportions of the photoresist pattern formed on the third bonding pads maybe relatively thin compared to portions of the photoresist patternformed on the first metal layer, so that the third bonding pads may bepartially removed during the anisotropic etching process.

The color filter layer may be formed by forming a color photoresistlayer on the planarization layer and then patterning the colorphotoresist layer. The color photoresist layer may be formed by a spincoating process, and stripe defects may occur in the color photoresistlayer by the second and third bonding pads during the spin coatingprocess.

Further, after forming the openings, a protective layer may be formed onthe backside surface of the substrate to protect the substrate.Particularly, the protective layer may be formed on the anti-reflectivelayer and inner side surfaces of the openings, and the substrate may beelectrically isolated from the bonding pads by the protective layer.However, the distance between the pixel regions and the micro lens arraymay be increased by the protective layer, and the sensitivity andcrosstalk of the backside illuminated image sensor may thus bedeteriorated.

SUMMARY

The present disclosure provides a backside illuminated image sensorhaving an improved structure and a method of manufacturing the backsideilluminated image sensor.

In accordance with an aspect of the present disclosure, a backsideilluminated image sensor may include a substrate having a frontsidesurface, a backside surface and a recess formed in a backside surfaceportion thereof, pixel regions disposed in the substrate, an insulatinglayer disposed on the frontside surface of the substrate, a bonding paddisposed on a frontside surface of the insulating layer, and a secondbonding pad disposed in the recess and electrically connected with thebonding pad.

In accordance with some embodiments of the present disclosure, thebackside illuminated image sensor may further include an anti-reflectivelayer disposed on the backside surface of the substrate.

In accordance with some embodiments of the present disclosure, theanti-reflective layer may include a first portion disposed on an innerside surface of the recess and a second portion disposed on a bottomsurface of the recess, and the second bonding pad may be disposed on thesecond portion of the anti-reflective layer.

In accordance with some embodiments of the present disclosure, theanti-reflective layer, the substrate and the insulating layer may have afirst opening, a second opening and a third opening for exposing aportion of a backside surface of the bonding pad, respectively, and thesecond bonding pad may be electrically connected with the bonding padthrough the first opening, the second opening and the third opening.

In accordance with some embodiments of the present disclosure, thebackside illuminated image sensor may further include a first spacerdisposed on inner side surfaces of the first, second and third openings.

In accordance with some embodiments of the present disclosure, thebackside illuminated image sensor may further include a second spacerdisposed on the first portion of the anti-reflective layer.

In accordance with some embodiments of the present disclosure, thebackside illuminated image sensor may further include a third bondingpad disposed on the second bonding pad, and a sum of a thickness of thesecond bonding pad and a thickness of the third bonding pad may besmaller than a depth of the recess.

In accordance with some embodiments of the present disclosure, thebackside illuminated image sensor may further include a light-blockingpattern disposed on the anti-reflective layer and having fourth openingscorresponding to the pixel regions.

In accordance with some embodiments of the present disclosure, thesecond bonding pad may be made of the same material as thelight-blocking pattern.

In accordance with some embodiments of the present disclosure, theanti-reflective layer may include a metal oxide layer disposed on thebackside surface of the substrate, a silicon oxide layer disposed on themetal oxide layer; and a silicon nitride layer disposed on the siliconoxide layer.

In accordance with an aspect of the present disclosure, a method ofmanufacturing a backside illuminated image sensor may include formingpixel regions in a substrate, forming an insulating layer on a frontsidesurface of the substrate, forming a bonding pad on a frontside surfaceof the insulating layer, partially removing a backside surface portionof the substrate to form a recess, and forming a second bonding pad inthe recess to be electrically connected with the bonding pad.

In accordance with some embodiments of the present disclosure, themethod may further include forming an anti-reflective layer on abackside surface of the substrate.

In accordance with some embodiments of the present disclosure, theanti-reflective layer may include a first portion formed on an innerside surface of the recess and a second portion formed on a bottomsurface of the recess, and the second bonding pad may be formed on thesecond portion of the anti-reflective layer.

In accordance with some embodiments of the present disclosure, themethod may further include partially removing the anti-reflective layer,the substrate and the insulating layer to form a first opening, a secondopening and a third opening which exposes a portion of a backsidesurface of the bonding pad.

In accordance with some embodiments of the present disclosure, themethod may further include forming a first spacer on inner side surfacesof the first, second and third openings.

In accordance with some embodiments of the present disclosure, formingthe second bonding pad may include forming a first metal layer on theanti-reflective layer, the first spacer and the portion of the backsidesurface of the bonding pad exposed by the first, second and thirdopenings, and patterning the first metal layer to form the secondbonding pad.

In accordance with some embodiments of the present disclosure, themethod may further include forming a third bonding pad on the secondbonding pad.

In accordance with some embodiments of the present disclosure, formingthe third bonding pad may include forming a second metal layer on thefirst metal layer, and patterning the second metal layer to form thethird bonding pad.

In accordance with some embodiments of the present disclosure, themethod may further include forming a light-blocking pattern havingfourth openings corresponding to the pixel regions on theanti-reflective layer, wherein the light-blocking pattern may besimultaneously formed with the second bonding pad.

In accordance with some embodiments of the present disclosure, a sum ofa thickness of the second bonding pad and a thickness of the thirdbonding pad may be smaller than a depth of the recess.

The above summary of the present disclosure is not intended to describeeach illustrated embodiment or every implementation of the presentdisclosure. The detailed description and claims that follow moreparticularly exemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments can be understood in more detail from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view illustrating a backside illuminatedimage sensor in accordance with an embodiment of the present disclosure;

FIG. 2 is an enlarged cross-sectional view illustrating ananti-reflective layer as shown in FIG. 1; and

FIGS. 3 to 15 are cross-sectional views illustrating a method ofmanufacturing the backside illuminated image sensor as shown in FIG. 1.

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention are described in moredetail with reference to the accompanying drawings. However, the presentinvention is not limited to the embodiments described below and isimplemented in various other forms. Embodiments below are not providedto fully complete the description of the present invention but ratherare provided to convey one aspect of the range of the present inventionto those skilled in the art.

In the specification, when one component is referred to as being on orconnected to another component or layer, it can be directly on orconnected to the other component or layer, or an intervening componentor layer may also be present. Unlike this, it will be understood thatwhen one component is referred to as directly being on or directlyconnected to another component or layer, it means that no interveningcomponent is present. Also, though terms like a first, a second, and athird are used to describe various regions and layers in variousembodiments of the present invention, the regions and the layers are notlimited to these terms.

Terminologies used below are used to merely describe specificembodiments, but do not limit the present invention. Additionally,unless otherwise defined here, all the terms including technical orscientific terms, may have the same meaning that is generally understoodby those skilled in the art.

Embodiments of the present invention are described with reference toschematic drawings of ideal embodiments. Accordingly, changes inmanufacturing methods and/or allowable errors may be expected from theforms of the drawings. Accordingly, embodiments of the present inventionare not described being limited to the specific forms or areas in thedrawings, and include the deviations of the forms. The areas may beentirely schematic, and their forms may not describe or depict accurateforms or structures in any given area, and are not intended to limit thescope of the present invention.

FIG. 1 is a cross-sectional view illustrating a backside illuminatedimage sensor 100 in accordance with an embodiment of the presentdisclosure.

Referring to FIG. 1, a backside illuminated image sensor 100, inaccordance with an embodiment of the present disclosure, may include asubstrate 102 having a frontside surface 102A and a backside surface102B, pixel regions 120 formed in the substrate 102, an insulating layer130 formed on the frontside surface 102A of the substrate 102, a bondingpad 132 formed on a frontside surface of the insulating layer 130, andan anti-reflective layer 160 formed on the backside surface 102B of thesubstrate 102. Particularly, the backside illuminated image sensor 100may include a recess 150 formed in a backside surface portion of thesubstrate 102 and a second bonding pad 186 formed in the recess 150 andelectrically connected with the bonding pad 132. Further, the backsideilluminated image sensor 100 may include a third bonding pad 192 formedon the second bonding pad 186, and the second and third bonding pads 186and 192 may be disposed in the recess 150.

The anti-reflective layer 160 may extend along an inner side surface anda bottom surface of the recess 150. That is, the anti-reflective layer160 may include a first portion 160A (refer to FIG. 9) formed on theinner side surface of the recess 150 and a second portion 160B (refer toFIG. 9) formed on the bottom surface of the recess 150. Further, theanti-reflective layer 160, the substrate 102 and the insulating layer130 may have a first opening 168, a second opening 170 and a thirdopening 172 to expose a portion of a backside surface of the bonding pad132, respectively. Specifically, the bonding pad 132 may be arranged tocorrespond with the recess 150, and the third opening 172 may be formedthrough the insulating layer 130 to expose the portion of the backsidesurface of the bonding pad 132. The second opening 170 may be formedthrough a bottom portion of the recess 150, and the first opening 168may be formed through the second portion 160B of the anti-reflectivelayer 160.

The second bonding pad 186 may be conformally formed to have a uniformthickness on the second portion 160B of the anti-reflective layer 160,inner side surfaces of the first, second and third openings 168, 170 and172, and the portion of the backside surface of the bonding pad 132. Thethird bonding pad 192 may be conformally formed to have a uniformthickness on the second bonding pad 186. Particularly, a sum of athickness of the second bonding pad 186 and a thickness of the thirdbonding pad 192 may be smaller than a depth of the recess 150, and thusthe third bonding pad 192 may be prevented from being protruded from therecess 150. For example, the second bonding pad 186 may be made of ametallic material, e.g., tungsten, and the third bonding pad 192 may bemade of a metallic material, e.g., aluminum. Further, though not shownin FIG. 1, a titanium layer and a titanium nitride layer serving as adiffusion barrier layer and an adhesive layer may be formed between thebonding pad 132 and the second bonding pad 186.

A first spacer 178 may be formed on the inner side surfaces of thefirst, second and third openings 168, 170 and 172, and a second spacer180 may be formed on the first portion 160A of the anti-reflective layer160. Particularly, the substrate 102 may be electrically isolated fromthe second bonding pad 186 by the second portion 160B of theanti-reflective layer 160 and the first spacer 178. That is, the secondbonding pad 186 may be disposed on the second portion 160B of theanti-reflective layer 160, the first spacer 178, and the portion of thebackside surface of the bonding pad 132 exposed by the first, second andthird openings 168, 170 and 172.

Further, the backside illuminated image sensor 100 may include alight-blocking pattern 188 disposed on the anti-reflective layer 160 andhaving fourth openings 190 (refer to FIG. 15) corresponding to the pixelregions 120. Particularly, the light-blocking pattern 188 may be made ofthe same material as the second bonding pad 186. For example, a tungstenlayer may be formed on the anti-reflective layer 160, and an aluminumlayer may be formed on the tungsten layer. The third bonding pad 192 maybe formed by patterning the aluminum layer, and the second bonding pad186 and the light-blocking pattern 188 may then be formed by patterningthe tungsten layer.

A planarization layer 194 may be disposed on the anti-reflective layer160 and the light-blocking pattern 188, and a color filter layer 196 anda micro lens array 198 may be disposed on the planarization layer 194.For example, the planarization layer 194 may be made of an insulatingmaterial such as silicon oxide or silicon nitride.

In accordance with the present embodiment, the second bonding pad 186and the third bonding pad 192 may be disposed in the recess 150, andthus stripe defects may be prevented from occurring during a photoresistcoating process for forming the color filter layer 196. Further, thethird bonding pad 192 may be prevented from being partially removedduring an etching process for forming the second bonding pad 186 and thelight-blocking pattern 188.

Each of the pixel regions 120 may include a charge accumulation region122 in which charges generated by the incident light are accumulated.The charge accumulation regions 122 may be disposed in the substrate102, and floating diffusion regions 126 may be disposed in frontsidesurface portions of the substrate 102 to be spaced apart from the chargeaccumulation regions 122.

The substrate 102 may have a first conductivity type, and the chargeaccumulation regions 122 and the floating diffusion regions 126 may havea second conductivity type. For example, a p-type substrate may be usedas the substrate 102, and n-type impurity diffusion regions functioningas the charge accumulation regions 122 and the floating diffusionregions 126 may be formed in the p-type substrate 102.

Transfer gate structures 110 may be disposed on channel regions betweenthe charge accumulation regions 122 and the floating diffusion regions126 to transfer the charges accumulated in the charge accumulationregions 122 to the floating diffusion regions 126. Each of the transfergate structures 110 may include a gate insulating layer 112 disposed onthe frontside surface 102A of the substrate 102, a gate electrode 114disposed on the gate insulating layer 112, and gate spacers 116 disposedon side surfaces of the gate electrode 114. Further, though not shown inFIG. 1, the backside illuminated image sensor 100 may include resettransistors, source follower transistors, and select transistorselectrically connected with the floating diffusion regions 126, in waysthat will be understood to those of ordinary skill in the art.

If the backside illuminated image sensor 100 is a 3T (or fewer thanthree transistors) layout, the transfer gate structures 110 may be usedas reset gate structures and the floating diffusion regions 126 may beused as active regions for connecting the charge accumulation regions122 with reset circuitries.

Each of the pixel regions 120 may include a frontside pinning layer 124disposed between the frontside surface 102A of the substrate 102 and thecharge accumulation region 122. Further, each of the pixel regions 120may include a backside pinning layer 128 disposed between the backsidesurface 102B of the substrate 102 and the charge accumulation region122. The frontside and backside pinning layers 124 and 128 may have thefirst conductivity type. For example, p-type impurity diffusion regionsmay be used as the frontside and backside pinning layers 124 and 128.

A first wiring layer 134 may be disposed on the insulating layer 130 andmay be electrically connected with the pixel regions 120. The firstwiring layer 134 may be made of the same material as the bonding pad132.

Further, a second insulating layer 140 may be disposed on a frontsidesurface of the insulating layer 130, the bonding pad 132 and the firstwiring layer 134, and a second wiring layer 142 may be disposed on thesecond insulating layer 140. A third insulating layer 144 may bedisposed on the second insulating layer 140 and the second wiring layer142, and a third wiring layer 146 may be disposed on the thirdinsulating layer 144. A passivation layer 148 may be disposed on thethird insulating layer 144 and the third wiring layer 146.

FIG. 2 is an enlarged cross-sectional view illustrating ananti-reflective layer as shown in FIG. 1.

Referring to FIG. 2, the anti-reflective layer 160 may include a metaloxide layer 162 disposed on the backside surface 102B of the substrate102, a silicon oxide layer 164 disposed on the metal oxide layer 162,and a silicon nitride layer 166 disposed on the silicon oxide layer 164.

The metal oxide layer 162 may function as a fixed charge layer. Forexample, the metal oxide layer 162 may function as a negative fixedcharge layer and include hafnium oxide (HfO₂), hafnium oxynitride(HfON), aluminum oxide (Al₂O₃), aluminum oxynitride (AlON), hafniumaluminum oxide (HfAlO) or hafnium aluminum oxynitride (HfAlON). In suchcase, negative charges of the negative fixed charge layer may form anegatively charged shallow minority carrier rich region, i.e., a holeaccumulation region, in a backside surface portion of the substrate 102,and the hole accumulation region may improve the function of thebackside pinning layers 128 (FIG. 1).

Referring again to FIG. 1, when the charge accumulation region 122 hasthe first conductivity type, that is, an n-type substrate is used as thesubstrate 102 and the charge accumulation region 122 include p-typeimpurities, the metal oxide layer 162 may function as a positive fixedcharge layer and include zirconium oxide (ZrO₂), hafnium silicon oxide(HfSiO₂), hafnium silicon oxynitride (HfSiON) or silicon nitride(Si₃N₄). In such case, the positive fixed charge layer may form anelectron accumulation region in a backside surface portion of thesubstrate 102.

Referring still to FIG. 1, the substrate 102 may be protected by theanti-reflective layer 160. In particular, the inner side surface and thebottom surface of the recess 150 may be protected by the first portion160A and the second portion 160B of the anti-reflective layer 160, andthe inner side surface of the second opening 170 may be protected by thefirst spacer 178. Further, the first spacer 178 may be disposed on theinner side surfaces of the first, second and third openings 168, 170 and172, and thus the metal oxide layer 162 of the anti-reflective layer 160may be electrically isolated from the second bonding pad 186 by thefirst spacer 178. For example, the first spacer 178 and the secondspacer 180 may be made of silicon oxide.

A solder bump 200 may be formed on the third bonding pad 192.Alternatively, a wire (not shown) may be bonded on the third bonding pad192. Further, the solder bump 200 may be disposed on a portion of thethird bonding pad 192 disposed in the recess 150 as shown in FIG. 1.Alternatively, the solder bump 200 may be disposed in the first, secondand third openings 168, 170 and 172.

FIGS. 3 to 15 are cross-sectional views illustrating a method ofmanufacturing the backside illuminated image sensor as shown in FIG. 1.

Referring to FIG. 3, device isolation regions 104 may be formed infrontside surface portions of a substrate 102 to define active regionsof the backside illuminated image sensor 100. The substrate 102 may havea first conductivity type. For example, a p-type substrate may be usedas the substrate 102. Alternatively, the substrate 102 may include abulk silicon substrate and a p-type epitaxial layer formed on the bulksilicon substrate. The device isolation regions 104 may be made ofsilicon oxide and may be formed by a shallow trench isolation (STI)process.

After forming the device isolation regions 104, transfer gate structures110 may be formed on a frontside surface 102A of the substrate 102. Eachof the transfer gate structures 110 may include a gate insulating layer112, a gate electrode 114 formed on the gate insulating layer 112 andgate spacers 116 formed on side surfaces of the gate electrode 114.Further, though not shown in figures, reset gate structures, sourcefollower gate structures and select gate structures may besimultaneously formed with the transfer gate structures 110 on thefrontside surface 102A of the substrate 102, in ways that will beunderstood to those having ordinary skill in the art.

Referring to FIG. 4, charge accumulation regions 122 used as pixelregions 120 may be formed in the substrate 102. In detail, chargeaccumulation regions 122 having a second conductivity type may be formedin the active regions of the substrate 102. For example, n-type chargeaccumulation regions 122 may be formed in the p-type substrate 102. Then-type charge accumulation regions 122 may be n-type impurity diffusionregions formed by an ion implantation process.

Then, frontside pinning layers 124 having the first conductivity typemay be formed between the frontside surface 102A of the substrate 102and the charge accumulation regions 122. For example, p-type frontsidepinning layers 124 may be formed between the frontside surface 102A ofthe substrate 102 and the n-type charge accumulation regions 122 by anion implantation process. The p-type frontside pinning layers 124 may bep-type impurity diffusion regions. The n-type charge accumulationregions 122 and the p-type frontside pinning layers 124 may be activatedby a subsequent rapid heat treatment process.

Referring to FIG. 5, floating diffusion regions 126 having the secondconductivity type may be formed in frontside surface portions of thesubstrate 102 to be spaced apart from the charge accumulation regions122. For example, the floating diffusion regions 126 may be n-type highconcentration impurity regions, which may be formed by an ionimplantation process. The transfer gate structures 110 may be arrangedon channel regions between the charge accumulation regions 122 and thefloating diffusion regions 126.

Referring to FIG. 6, an insulating layer 130 may be formed on thefrontside surface 102A of the substrate 102, and a bonding pad 132 and afirst wiring layer 134 may be formed on the insulating layer 130. Theinsulating layer 130 may be made of an insulating material such assilicon oxide, and the bonding pad 132 and the first wiring layer 134may be made of a metallic material such as copper or aluminum. Forexample, after forming the insulating layer 130, a metal layer (notshown) may be formed on the insulating layer 130, and the bonding pad132 and the first wiring layer 134 may then be formed by patterning themetal layer.

A second insulating layer 140 may be formed on the insulating layer 130,the bonding pad 132 and the first wiring layer 134, and a second wiringlayer 142 may be formed on the second insulating layer 140. A thirdinsulating layer 144 may be formed on the second insulating layer 140and the second wiring layer 142, and a third wiring layer 146 may beformed on the third insulating layer 144. A passivation layer 148 may beformed on the third insulating layer 144 and the third wiring layer 146.The first, second and third wiring layers 134, 142 and 146 may beelectrically connected with the pixel regions 120, and the bonding pad132 may be electrically connected with the first, second and thirdwiring layers 134, 142 and 146.

Referring to FIG. 7, a back-grinding process or a chemical andmechanical polishing process may be performed in order to reduce athickness of the substrate 102. Further, backside pinning layers 128having the first conductivity type may be formed between a backsidesurface 102B of the substrate 102 and the charge accumulation regions122. For example, p-type impurity regions functioning as the backsidepinning layers 128 may be formed by an ion implantation process, and maythen be activated by a subsequent laser annealing process.

Alternatively, the backside pinning layers 128 may be formed prior tothe charge accumulation regions 122. For example, after forming thebackside pinning layers 128, the charge accumulation regions 122 may beformed on the backside pinning layers 128, and the frontside pinninglayers 124 may then be formed on the charge accumulation regions 122. Insuch case, the backside pinning layers 128 may be activated by the rapidheat treatment process along with the charge accumulation regions 122and the frontside pinning layers 124. Further, the back-grinding processmay be performed such that the backside pinning layers 128 are exposed.

Meanwhile, when the substrate 102 includes a bulk silicon substrate anda p-type epitaxial layer formed on the bulk silicon substrate, thecharge accumulation regions 122 and the frontside and backside pinninglayers 124 and 128 may be formed in the p-type epitaxial layer, and thebulk silicon substrate may be removed by the back-grinding process.

Referring to FIG. 8, the substrate 102 may be partially removed so as toform a recess 150 corresponding to the bonding pad 132 in a backsidesurface portion of the substrate 102. For example, a first photoresistpattern 152 may be formed on the backside surface 102B of the substrate102, which exposes a portion of the backside surface 102B of thesubstrate 102 to correspond to the bonding pad 132. The recess 150 maybe formed by an anisotropic etching process using the first photoresistpattern 152 as an etching mask. The recess 150 may have a larger widththan the bonding pad 132, and the anisotropic etching process forforming the recess 150 may be performed for a predetermined time so thatthe recess 150 has a predetermined depth. The first photoresist pattern152 may be removed by an ashing or stripping process after forming therecess 150.

Referring to FIG. 9, an anti-reflective layer 160 may be formed on thebackside surface 102B of the substrate 102, and an inner side surfaceand a bottom surface of the recess 150. Accordingly, the anti-reflectivelayer 160 may include a first portion 160A formed on the inner sidesurface of the recess 150 and a second portion 160B formed on the bottomsurface of the recess 150. For example, a metal oxide layer 162, asilicon oxide layer 164 and a silicon nitride layer 166 may besequentially formed on the backside surface 102B of the substrate 102,and the inner side surface and the bottom surface of the recess 150. Themetal oxide layer 162 may be formed by a metal organic chemical vapordeposition (MOCVD) process or an atomic layer deposition (ALD) process,and the silicon oxide layer 164 and the silicon nitride layer 166 may beformed by a chemical vapor deposition (CVD) process.

Referring to FIG. 10, the anti-reflective layer 160, the substrate 102and the insulating layer 130 may be partially removed so as to form afirst opening 168, a second opening 170 and a third opening 172 throughwhich partially expose a backside surface of the bonding pad 132. Forexample, a second photoresist pattern 174 may be formed on theanti-reflective layer 160, which partially exposes the second portion160B of the anti-reflective layer 160. The first opening 168, the secondopening 170 and the third opening 172 may be formed by an anisotropicetching process using the second photoresist pattern 174 as an etchingmask. The second photoresist pattern 174 may be removed by an ashing orstripping process after forming the first opening 168, the secondopening 170 and the third opening 172.

Referring to FIG. 11, a spacer layer 176 may be formed to have a uniformthickness on the anti-reflective layer 160, inner side surfaces of thefirst, second and third openings 168, 170 and 172, and a portion of thebackside surface of the bonding pad 132 exposed by the first, second andthird openings 168, 170 and 172. For example, the spacer layer 176 mayinclude silicon oxide and may be formed by a CVD process.

Referring to FIG. 12, the spacer layer 176 may be partially removed toform a first spacer 178 and a second spacer 180. The first spacer 178may be formed on the inner side surfaces of the first, second and thirdopenings 168, 170 and 172, and the second spacer 180 may be formed onthe first portion 160A of the anti-reflective layer 160. For example,the spacer layer 176 may be partially removed by an anisotropic etchingprocess. Particularly, a portion of the spacer layer 176 disposed on thebackside surface 102B of the substrate 102 may be fully removed whileforming the first and second spacers 178 and 180.

Referring to FIG. 13, a first metal layer 182, e.g., a tungsten layer,may be formed on the anti-reflective layer 160, the first and secondspacers 178 and 180, and the portion of the backside surface of thebonding pad 132 exposed by the third opening 172, and a second metallayer 184, e.g., an aluminum layer, may be formed on the first metallayer 182. Particularly, a sum of a thickness of the first metal layer182 and a thickness of the second metal layer 184 may be smaller than adepth of the recess 150.

Referring to FIG. 14, a third bonding pad 192 may be formed bypatterning the second metal layer 184 as shown in FIG. 14. For example,a third photoresist pattern (not shown) may be formed on the secondmetal layer 184, and the third bonding pad 192 may be formed by ananisotropic etching process using the third photoresist pattern as anetching mask.

Referring to FIG. 15, a second bonding pad 186 and the light-blockingpattern 188 may be formed by patterning the first metal layer 182.Particularly, the second and third bonding pads 186 and 192 may bearranged in the recess 150. Specifically, the second bonding pad 186 maybe formed on the backside surface portion of the bonding pad 132, thefirst spacer 178 and the second portion 160B of the anti-reflectivelayer 160, and the third bonding pad 192 may be formed of the secondbonding pad 186. The light-blocking pattern 188 may be formed on theanti-reflective layer 160 and may have fourth openings 190 correspondingto the charge accumulation regions 122.

For example, a photoresist layer (not shown) may be formed on the firstmetal layer 182 and the third bonding pad 192, and then a fourthphotoresist pattern (not shown) may be formed by a photolithographyprocess. The second bonding pad 186 and the light-blocking pattern 188may be formed by an anisotropic etching process using the fourthphotoresist pattern as an etching mask. Because a top surface of thethird bonding pad 192 is positioned lower than that of theanti-reflective layer 160, a thickness of a portion of the fourthphotoresist pattern formed on the third bonding pad 192 may berelatively thick. Accordingly, damage to the third bonding pad 192 maybe sufficiently prevented while forming the second bonding pad 186 andthe light-blocking pattern 188.

Referring again to FIG. 1, a planarization layer 194 may be formed onthe anti-reflective layer 160 and the light-blocking pattern 188, and acolor filter layer 196 and a micro lens array 198 may be sequentiallyformed on the planarization layer 194. The planarization layer 194 maybe made of an insulating material such as silicon oxide or siliconnitride.

The color filter layer 196 may include red filters, blue filters andgreen filters. Each of the filters may be formed by forming a colorphotoresist layer and then performing a photolithography process.Because the top surface of the third bonding pad 192 is positioned lowerthan that of the planarization layer 194, stripe defects may beprevented from occurring while forming the color photoresist layer.

Although the backside illuminated image sensor and the method ofmanufacturing the same have been described with reference to specificembodiments, they are not limited thereto. Therefore, it will be readilyunderstood by those skilled in the art that various modifications andchanges can be made thereto without departing from the spirit and scopeof the present disclosure defined by the appended claims.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

1. A backside illuminated image sensor comprising: a substrate having afrontside surface, a backside surface and a recess formed in a portionof the backside surface; a plurality of pixel regions disposed in thesubstrate; an insulating layer disposed on the frontside surface of thesubstrate, the insulating layer defining a frontside surface; a bondingpad disposed on the frontside surface of the insulating layer; and asecond bonding pad disposed in the recess and electrically connectedwith the bonding pad.
 2. The backside illuminated image sensor of claim1, further comprising an anti-reflective layer disposed on the backsidesurface of the substrate.
 3. The backside illuminated image sensor ofclaim 2, wherein the anti-reflective layer comprises a first portiondisposed on an inner side surface of the recess and a second portiondisposed on a bottom surface of the recess, and the second bonding padis disposed on the second portion of the anti-reflective layer.
 4. Thebackside illuminated image sensor of claim 3, wherein theanti-reflective layer, the substrate and the insulating layer include afirst opening, a second opening and a third opening for exposing aportion of a backside surface of the bonding pad, respectively, and thesecond bonding pad is electrically connected with the bonding padthrough the first opening, the second opening and the third opening. 5.The backside illuminated image sensor of claim 4, further comprising afirst spacer disposed on inner side surfaces of the first, second andthird openings.
 6. The backside illuminated image sensor of claim 3,further comprising a second spacer disposed on the first portion of theanti-reflective layer.
 7. The backside illuminated image sensor of claim2, further comprising a third bonding pad disposed on the second bondingpad, wherein a sum of a thickness of the second bonding pad and athickness of the third bonding pad is smaller than a depth of therecess.
 8. The backside illuminated image sensor of claim 2, furthercomprising a light-blocking pattern disposed on the anti-reflectivelayer and having fourth openings corresponding to the pixel regions. 9.The backside illuminated image sensor of claim 8, wherein the secondbonding pad is made of the same material as the light-blocking pattern.10. The backside illuminated image sensor of claim 2, wherein theanti-reflective layer comprises: a metal oxide layer disposed on thebackside surface of the substrate; a silicon oxide layer disposed on themetal oxide layer; and a silicon nitride layer disposed on the siliconoxide layer.
 11. A method of manufacturing a backside illuminated imagesensor, the method comprising: forming a plurality of pixel regions in asubstrate; forming an insulating layer on a frontside surface of thesubstrate; forming a bonding pad on a frontside surface of theinsulating layer; partially removing a backside surface portion of thesubstrate to form a recess; and forming a second bonding pad in therecess to be electrically connected with the bonding pad.
 12. The methodof claim 11, further comprising forming an anti-reflective layer on abackside surface of the substrate.
 13. The method of claim 12, whereinthe anti-reflective layer comprises a first portion formed on an innerside surface of the recess and a second portion formed on a bottomsurface of the recess, and the second bonding pad is formed on thesecond portion of the anti-reflective layer.
 14. The method of claim 12,further comprising partially removing the anti-reflective layer, thesubstrate and the insulating layer to form a first opening, a secondopening and a third opening that are each configured to expose acorresponding portion of a backside surface of the bonding pad.
 15. Themethod of claim 14, further comprising forming a first spacer on each ofa set of inner side surfaces corresponding to the first, second andthird openings.
 16. The method of claim 15, wherein forming the secondbonding pad comprises: forming a first metal layer on theanti-reflective layer, the first spacer and the portion of the backsidesurface of the bonding pad exposed at the first, second and thirdopenings; and patterning the first metal layer to form the secondbonding pad.
 17. The method of claim 16, further comprising forming athird bonding pad on the second bonding pad.
 18. The method of claim 17,wherein forming the third bonding pad comprises: forming a second metallayer on the first metal layer; and patterning the second metal layer toform the third bonding pad.
 19. The method of claim 17, furthercomprising forming a light-blocking pattern including fourth openingscorresponding to the pixel regions on the anti-reflective layer, whereinthe light-blocking pattern is simultaneously formed with the secondbonding pad.
 20. The method of claim 17, wherein a sum of a thickness ofthe second bonding pad and a thickness of the third bonding pad issmaller than a depth of the recess.